Investigating the mechanisms of polymer crystallization by SAXS experiments

Abstract

The importance of SAXS experiments for studies of the basic mechanisms of polymer crystallization and melting is demonstrated with four examples. (1) Time and temperature dependent measurements on s-PP during isothermal crystallization and melting yield the dependencies between crystallization temperature, crystal thickness, crystallization rate and melting point. Results show that the lamellar crystallites form in a two-step process, (2) Time dependent experiments on crystallizing PE enable the crystal thickening to Le followed from the beginning and confirm the logarithmic law. (3) Temperature dependent studies on PE during cooling or heating prove that secondary crystallization here is based on a surface crystallization and melting mechanism. (4) The cross-hatching in i-PP has a characteristic signature in the SAWS-curve. Data evaluation yields the total length per unit volume of the edges along the intersections of the crystallites.